Control system



May 7, 1946. w. D. HALL 2,399,673

l CONTROL SYSTEMv 1 Filed June 29, 1.943 s sheets-sheet 1 Takara INVENTOR.

l May 7, 1946. w. D. HALL CONTROL `swrsrxlm Filed June 29, 1943 3 sheets-snaai 2 w. D. HALL CONTRUL SYSTEM Maly 7, 1946.l

stantially greater than Patented'uMay 7,1946

UNITED STATES rlAlllNl" OFFICE I' l 2,399,613 i Y y TCONTRLSYS'TEM i will@ nfn'au, Eudnsw. vs., signor a Y Nathan r. Hsu. Madison. N. J. paesana- June '2a.` 194s, sei-uu No. 492,131 '2.1 cisim'sj (ci. 15s-2a) This invention relates to controlsystems and moreparticularly to means for igniting, burning, regulating the combustion oi',y and otherwise controlling -combustionV of iuel. lThe primary' object of'this" invention 'resides' in the provision' of a` system' for igniting and/or regulating a fuel burner, that is simpler compact. and low in cost as compared-with systems of the prior art. Other objects include the provision of means for causing the control functions ofthe system to be perwhereby the probability of ignition oi' fuel issubventors in the past.-

- As a general ruie, a combustion control system livery of thatfuel Vin such a manner that it will be burned thout violent explosions or other dangerous conditions.` To -achieve these two main functions the prior .art` control 'systems as proposed by others have been qultecomplicated and expensive, and moreover as a further general rule they employed external control boxes containing numerous externalcontrol parts such as relays. tranSIormeraand the like, whichl are unnecessary with my preferred form of invention. While such parts can be applied to my control system and still fall within the broadest aspects of my invention. it will be clear that thenovel mode of operation and structural construction is such that these parts are not absolutely necessary as they are in many prior art devices.

Brieily speaking, the preferred form of my inlverition includes an electrical igniter, or other heater, which is heated initially. A thermostatic achieved by other intwo members relative to which slipping occurs do slip, the circuit to the ignlter is broken.A The foregoing briefexplanation is not intended to formed at a rapid rate and in a safe manner.

- Still other objects include the provision" of means be particularly comprehensive, and certain variajtions are hereinai ter described. Thejprinciple oi my invention is. however, broader than the details of the particular systems shown, which are merely illustrative, and accordingly the claims are wordedv broadly to cover the principle generically.

This application is a continuation-impart of myu prior copending application. Serial Number 347,951. led July 27, 1940, entitled Control systems. Figures 1. 2, 3 and 410i this application and the description of these figures are shown and found in substance. in the said prior co- Vpending case.v

In the drawings: Figure 1 is aV schematic diagram of the parts making up one forrn of this invention 'with certain parts oi the fuel tlow path and combustion control parts illustrated in section.

, Figure 2 illustrates certain thermostatc clutches used with the burner of Figure 1.

Figure 3 illustrates anotherjiorm of combustion control system claimed in this application.

element is heated by that igniter or other heater.

ment. or it may be the second contact which is arranged to slip with respect to the stationary support for the whole system, or it may be the thermostatic element itself which is arranged to slip with respect to the stationaryl 4supllui't for the whole system. A In any event, contacts in the igniter circuit are arranged such that when the Figure 4 isa drawing of still another form ci combustion control system claimed herein.

Figure 5 illustrates still another form of combustion control system claimed herein.

Figure 6 illustrates still another form of combustion control system claimed herein.

Figure '7 is a sectional view of Figure 6 taken along line 6 6,

Since the details of the burner, Ian and fuel pump, are oi little importance to an understanding of the .principle claimed in this application. I will merely mention the function of the various Parts making up those elements, and refer those skilled in the art to my prior application in event they desire complete descriptions oi those parts. In Figures 1 and 2il a fuel tank I0, has a fuel feed line il: a mixer I2, combustion chamber i3, ceramic leat retaining re-igniter I4, igniter of the hot-wire type i5, radiator I6, Il, exhaust pump iland exhaust outlet 16. An electric motor M drives a shaft 43 which in turn drives the discs 2| and 22 of two thermostatic clutches respectively. These thermostatic clutches respectively include bimetallic strips 2li and 23, and secondarydiscs I! and 24 whichrespectively are attached to shafts 43e and 15. These latter shafts respectively drive pump I8 and circulating fan 26. Ears 4I and 45 on discs 2| and 2l provide means for engagement of the bimetallic strips 20 and 23 respectively. When the temperature of the system is very low, bimetalilc strip 23 is out of engagement with ear 45, but bends to make such ento either a burner as shown, an open air burner,

or any other kind of burner. In the particular burner shown, the pump I8 is employed to pump out the exhaust gasses at such a high rate that fuel is drawn in the fuel feed line. The pump I3 may be located in the fuel feed line Il, or may be replaced by a solenoid-operated gas valve when gas is burned, such gas valve being represented in Figure 4 for example as M. The part M, may therefore be a motor-driven pump. or a gas valve, or other equivalent fuel flow controller.

Passing 'now from the parts, described above. to the heart of the invention, which is claimed, I refer to Figure 1 which employs a single bimetallic element 33 with a contact 33a carried by the upper end thereof. The lower end of the bimetallic strip 33 is rigidly supported by a fixture 3l which may be part of some xed piece of apparatus such as a housing. In general the location of the strip 33 with respect to the radiator I1 is such that it responds to heat from that radiator, and the distance of separation is not important so long as substantial heat is received by strip 33, although if the strip isplaced immediately adjacent the radiatorthe system is more compact than it might otherwise be. The control system has two other parts that are rigidly'supported solely at one end. The square rod 32 is rigidly fixed at its left end, and is solid stainless steel. 'I'he contact arm 23 is rigid and is xed at its upper end 21. It is understood, therefore, that the three rigidly xed parts, namely 21, 32,'and 34 have a fixed relationship to each other. I'he only movable parts are (a) the free or outer end of strip 33 which moves only when the temperature of strip 33 changes, and (b) the movable block 3U. Block 30 is rather heavy and has a hole in it slightly larger than the size of rod 32. It also has aninsulating section 3l of suitable insulating material such as porcelain or steatite. Other than for the insulating piece 3l, the block 30, as well as rod 32, is made of stainless steel or other material suitable to withstand the necessary temperatures without rusting. Block 30 carries a contact point 30a. which is arranged to engage or disengage contact arm 28 depending on the motion of block 30. No springs or other force producing devices, except strip 33. act upon block 30 and therefore friction between the block and rod 32 tends to cause the block 30 toremain in any position to which it is pushed by strip 33. Initially, when the heater is in its "on" position and the system is cool, the strip 33 is curved slightlyand the free end is in engagement with insulating block 3i. This action maintains contact between 23 and 30a. The strip 33 is arranged to receive heat not only from radiator i1, but from resistor 29 which is rather closely associated with strip 33.

The operation of the combustion control system of Figure 1 is as follows: When a potential is aseaeva applied across wires 35 and 36 such as by the mere closing of a switch, time clock, or room thermostat (any of winch may be connected at 3| current flows through the following path: 35, 32,

3|), 30a, 28, 43, I5, 29, 35. Since at this stage of the operation contact 33a is out of contact with block 30, no current flows to the motor M. However. after a short time heat from resistor 29 iiexes strip 33 to such an extent that contact 33a moves into lcontact with vblock4 30 and this establishes a second current path in addition to the first; the second path being: 3'5, 32. 30,33a, 33, 3l. 33, M, 31, 36. Since the block 33 is rather heavy it will not begin to move instantly but the strip 33 must be heated considerably before it has sufcient force to overcome the static friction of this block and move the same enough' to break the circuit at 2 B-30a. Hence the igniter is energized for a few seconds or more after fuel begins to flow. If the ame satisfactorily ignites. the high heat of the flame will supply ample force to break contacts 23-3|la quickly and therefore the igniter wire I5 and resister 29 are deenergized but of course contact 33a continues to press against block 30 and maintain the motor circuit closed. As the burner continues to heat the strip 33 the latter will continue to move block 30 toward the right due topressure exerted on block 33 by the contact 33cm. Should the flame then for any reason be come extinguished. the strip.33 will begin to cool and reverse its direction of motion. Its contact 33a will leave engagement with block 33 within a short interval of time. I prop ortion the block 3U as to weight, the strip 33 as to thickness, and the ceramic re-igniter as to mass, so that the ceramic re-igniter will remain suiiiciently hot to ignite the fuel even after strip 33 has broken its circuit at 33a. Hence should the flamebecome extinguished it would not be possible to start the motor unless the re-igniter Il, or the main igniter I5, is suiliciently hot to ignite the fuel. For example. if the re-igniter Il is massive enough to relight the flame after the latter has been extinguished 30 seconds, I proportion the weight oi' block 30 and the thickness as well as the width of strip 33 so that upon cessation of combustion the circuit at Sil-33a is broken in a time substantially less than 30 seconds. Should the fuel fail to ignite throughout a period of more than thirty seconds, strip 33 will after perhaps a minute or so engage insulating piece SIL Still further cooling of the heater will take place and strip 33 will push the block 30 to the left due to its contact `with 3i until finally, after several. minutes, contact 30a re-engages contact 23 so that the igniter circuit is reestabiished via the circuit 35-32 33--3lla-2 8-21-40-I 5-2 9-36. The motor M at this time is deenergized, but as heater 29 again raises the temperature of 33, contact at 33o- 30 is again made with a consequent restarting of the motor and reestablishing flow of fuel which will be relighted by the hot igniter I5.

The above description of operation presumed that the fuel supply was properly ignited by the ig'niter I5 and that fuel then continued to burn for at least a `short while. I will now describe the operation of my system under the abnormal condition (but a condition that does sometimes occur) of failure in the ignter i5 to actually ignite the fuel on the first effort. Assume that the apparatus is in its "oli" position with strip 33 solidly against the insulating piece 3i. Hence contact is made at 28-30a but broken at all-33a. Upon control switch 9| being closed, current begins to flow through the resistor 29 as heretofore specified and this causes strip 3l to flex to the position shown in Figure l. The motor M now starts and fuel passes to the combustion chamber. If the fuel fails to ignite, heater 20 will after an additional time cause strip tl to flex enough to push block 30 away from contact 28 thus breaking the igniter circuit. This action deenergizes resistor It and soon thereafter the strip 33 begins to cool. Such cooling breaks the motor circuit at 33o-It and the strip lt will continue to cool until it engagesdl and then nnallv forces block 30 to the left to reclose the igniter circuit at 2-Ila. The resistor 2l is again heated and again causes flexure of strip to the right until the motor circuit is again made at 33o-III. If my circuit is carefully studied. in view of the above explanation, it will become apparent that the control system will repeatedly energize the ignlter It and motor M. The sequence will be as follows: igniter on," fuel on," attempt at ignition." "ign-iter oil, "fuel off, time space to permit unb'urnt gas to escape," "igniter on,fuel on attempt-at ignition, igniter oil'," "fuelofi',

j'time space to permit`unburnt gas to escape." igniteronf etc., indenitely or until stopped by a suitable safety cut-out (not shown) such as that in casing 13 of my prior Patent 2,159,658.

Buch a safety switch may be located at point 91 in Figure l.

So far as the combustion control systems illustrated herein are concerned. the motor M may be a solenoid valve located in the path of fuel as in sleeve much longer in a direction parallel to the shaft than the arm I2 in such direction. The arm t2 carries a contact 51a. The stationary contact point it is arranged to cooperate with movable contact 82a. Another bimetallic strip 5l may be employed, although this strip can satisfactorily be composed of an ordinary rigid metal as under normal conditions the operation of the system does -not depend upon ilexure of this strip. The strip t1 is composed of a, thick piece of bimetal and denects to the dotted line position at a temperature of about 50 F. At normal tempeintures it is straight or at least curved downtion. It a strip 51 of rigid ordinary metal is used,

it is possible for the ambient temperature to fall v4so low. -50 l1'.v for example, that strip 33'- will strike 'strip l1 rand upon further fallin temperature internallystressitself to such a large extent i as to takeon permanent deformation. Since it the case of my said prior Patent 2,159,658, provided some meansis provided to force the gases through the system. l

In addition to other safety precautions mentioned in this patent, overheatingthermostats such as 82, may be connected in wire I6. Buch thermostats -may be located near any part of the system that is liable to become overheated, for example the fuel tank I0.

While the system of Figure 3 is very eilective for many purposes'. it is particularly'useful in systems subjected to considerable jarring, and it uses a lost-motion or slip-friction switch having rotary motion instead of linear motion. In Figure 3, a central rigidly supported shaft 50 is composed of stainless steel. An outer sleeve has a diameter slightly larger than shalt 5t and is arranged to freely slip around the shaft 60. A spring t4 bears downwardly on sleeve Il and places considerable contact pressure between the sleeve Si and the shaft it. Spring 94 does not engage either the arm t2 or bimetal Il' as this spring bears against a portion of sleeve ti whichis in front of the strip Il' and sleeve-arm 52. Spring 9| may be omitted from the construction if desi ed with good operation, since the sleeve Si and rod 60 may be provided with a proper amount of friction without the spring 8l, The strip 33', I have found, may be rather heavy and one specimen device 'has a strip 3l' approximately one-half inch wide, 0.05 inch thick. and of five inches developed length.

The coiled bimetallic element 38 is composed preferably of the highest quality heat withstandlng bimetal and has an inner end rigidly bolted or welded to the sleeve 5i. The outer end of this oimetaliic strip carries a contact point B3. A sta- .ionary contact point 54 supported by the rigid :lock 5S cooperates with contact B3. The sleeve ii carries an arm 52 which arm is relatively lighty is compared to the total weight of the sleeve 5|. ihis relationship may be effected by making the is necessary for the ambient temperature-to fall approximately F.- aiter the end of 53 strikes 51- before the 'strip It would be permanently stressed in event strip El was of rigid metal, the outer end of strip u' will touch t1 at room temperatures and exert a slight tension against 51. This small tension will not permanently deform the resilient bimetallic strip 33. Contacts 62a, 56 are therefore closed at ordinary room temperatures. but contacts 53-54 open. The wire 36' is a ilexible lead and fastens to arm 52; however, the wire It' does not have any4 spring action or in any way mechanically exert a force directly upon arm 52: it merely connects electrically thereto.

Upon applying potential to wires 35, 36 while the apparatus is in the initial ci! position, only one current path exists, namely: lt -29- N-Ha-SB'. Heat from resistor 29 affects strip 33' and causes the same to tend to coil up. .This will not break the circuit at b2c-lt at this time inasmuch as the friction between 50 and 5i is appreciable and will tend to hold the position shown until a denite torque is exerted on the sleeve Ii by the bimetallic strip I3'. The contact 5I moves through midair until it strikes contact point il. During this time, prior to striking this contact point, itv is clear that strip It' cannot exert a torque on the sleeve 5i. Finally as* resistor 20 gets strip t3' hotter and hotter the contact $3 moves into engagement with stationary contact t4 and this engagement closes the motor circuit via the following current path: 4-M-tt-64-53-33'-5|5236'. For a time after this, both the motor M and the ignlter It operate simultaneously, The time during which the two operate simultaneously is governed by the tension in spring 8|. If this spring causes considerable tension between sleeve 5I and rod Ill, the igniter il and the motor M will opcrate simultaneously vfor a long time. Another method of .obtaining 4a long simultaneous operation o! those parts is to have resistor 29` Just powerful enough te barely heat strip sa' to the point where the circuit between 52a and t6 is broken. Preferably, the tension and/or heating is so arranged so that the motor M and igniter it operate simultaneously for the time deemed best for the particular style of burner to which 'the invention is applied. which in general is about 15 to 30 seconds. As Just stated, the lgniter I! and motor M operate simultaneously for a while. If

the fuel ignltes, heat will be supplied to strip 3l' from the combustion chamber and this strip will continue to dex. Since contact il has now struck a rigid obstruction l further ilexure of the strip will result in rotation o1 the sleeve El against the frictlomof stationary shaft 50. Consequently arm 52 will be rotated counterclockwise and contact between 52a and 56 broken. This deenergizes the igniter l5 and resistor 2U.. 'Further heating will continue to rotate arm I2 counterclockwise and contacts Si and Il will remain in engagement. If the heater i1 becomes rather hot and then the ow of fuel ceases, the friction between 60 and 5l will be sumcient to hold arm 52 in the position it had when the flame went out. Cooling of 33' will therefore result first in a counterclockwise rotation of contact point $3, and a quick disengagement of 53 and M. However, such rotation is limited as the free end of strip 3J' strikes 51 alter rotating clockwise a fraction of an inch. As soon as strip I3' strikes 5l the subsequent fiexure of strip 33 will result in a clockwise'rctationof arm 52 with slippage vtaking piace at Bil, El. Strip 51 will ilnally return to a straight position from its high temperaturey condition and as strip 23' approaches room temperature its contacts 52d-66 will be reclosed. This closure will reclose the ignlter circuit- Il, reenergize resistor 28, reheat Il' which strip will be gin to rotate 53 clockwise without any slippage taking place at Sil-5I. reclose ik, 'restart the motor, and subsequently reopen the circuit to the igniter at Ent-56. Hence an attempt at reignition .will be made. Should this attempt to relight the fuel fail, additional attempts will automatically he made. Unless n 'thermal cutout such as that contemplated by reference `i3 of my prior Patent 2,159,658, is placed in lead line 35, the igniter and fuel motor will operate intermittently and make repeated attempts indeliniteiy to ignite the fuel. If such a cut-out is used, the number of attempts will be limited to several attempts.

Briefly speaking. thepsequence of operation under practically all conditions is the same ior Figure 3 as for Figure l. However, Figure 3 shows an additional optional feature now to be described in this paragraph. After being placed into operation, when the heating system reaches a predetermined temperature, the bimetallic switch Il closes to 8G starting an added Ian motor 6] that is also energized from wires I5 and 36. This fan motor Bl has a fan totally independent of motor M and may replace fan, 28 if desiredor it maybe used together with fan 28. However, the two normally need not both be used. The cooling effects of ian l2 are such as to tend to hold bimetallic strip 33' at apredetermined maximum temperature and this may be accomplished if ian l2 is a small fan that blows cold air in small quantity over strip Il' if the latter exceeds the said maximum temperature; As pointed out in my aforesaid copending application S. N. 347,951, the operation of the main fan 26 will hold the system at a predetermined maximum temperature under most circumstances' perature, theA system acts more quickly than it otherwise would in relighting the burner after the flame goes out.

The control system of Figure 4 will now be described in detail. The apparatus of Figure 4 is shown in section in the drawings and has a shaft 50, said shaft being xed at the rear end thereof. Sleeve 5| is arranged to slip over' the shaft as the sleeve has a' very slightly larger diameter than the shaft. The spring 94 is located in front of bimetailic'strip 33' and presses firmly on sleeve 5l (which obviously extends well in front of strip Il' as sleeve 5i is sectioned whereas the strip Il' is shown'ln full view). The arm 52 is fastened `electrically and mechanically to sleeve Si and extends behind blmetallic strip 23' and carries a contact 62a. The bimetallic strip is arranged to coil up when heated and to uncoil when cooled. A stationary support il supports screw I8, the latter carrying on its tip end a contact 'point 69. Another stationary contact, not electrically connected, is provided at 56. A stationary square bar 6B supports a large movable block Si.

`A contact point 84 is fastened to the biockil:

resistor 28 becomes heated and causes strip 33' to coil up until contact 63 engages This causes motor (or valve) M to be energized via the following circuit: 3652-33'83465- B6M8l93-9435- For an interval the motor M and lghiter I5 will simultaneously operate thus ignitlng the fuel. Further heating of 3l due to heat from the llame (or 25) will result in further coiling up of 23'. Since block B5 is very heavy, slippage will take place at 50--51 before will slip. Hence contacts 6B-52a will be broken and arm 52 will move into engagement with I6. Since 66 is stationary, the slippage will now take place at Gil-66 and as the burner continues to heat, the block will slip along 66 with 83 and M maintaining contact. 4An arm 90 is pivoted near its'center at U2. It carries on its lower end a contact point 83. A complementary stationary contact point B4 connects to wire-I5. A spring 9i tends to produce clockwise motion of the arm and vthereby normally maintain the contacts ll and Il together, When overheating takes place block 85 moves to the left, engages arm 90, rotates the latter. and breaks the motor circuit at 8l, B4. If spring Il is omitted the system cannot be restarted without manually resetting arm 00. With spring 9i connected, the system will restart automatically when strip 33' cools.

Shouldfthe burner satisfactorily ignite and burn for a long while, then the flame be accidentally extinguished, 6I will immediately drop away from El and rotate counterclockwise until it comes into contact with 65a. Strip il' will tend to further uncoll and reclose 52o-69 thus reenergizing the igniter circuit I5. Heater 28 will reheat 33' thus recloslng B3 and 8l restartlng the motor M. Should the llame fail to relight, the heat from 29 will tend to further coil up 33 so as to break the circuit at Ent-6l. This willcause 33'. to cool and move into engagement with 85a.' Further cooling will take place thus redonne szaf-ss and this wm resent ze and 33' thereby making another attempt at ignition. As a result. repeated ignition attempts are made. The same holds true in event an original attempt at ignitioni'ails; that is several attempts to ignite willbe made if the ilrst eilort i'ails. ShouldI it be deemed desirable, suitable safety switches such as overheating thermostats, time clocks, or switches like in casing 13 of my said prior Patent 2,159,658, may be placed in line 33.

The best mode oi utilizing the control system the gas at'oniy a few ports at the extreme'right end, the automatic system at the left end, in-

cluding strip 33', will not be heated by the flame and that mechanism will operate in the manner it would in event there was no ignition at all, namely, 4igniter off," fuel oil," "time to permit clockwise. by overcoming the friction between sleeve .and rod 253 and spring 294. Should the thermostat T cease'calling tor heat by brealing its circuit, the heater 2|5 Will be immediately deenergized. Since vstrip 233 is heated by the flame 'and heater 2|5, and' the latter source of heat has been'cut oil', the strip 233 will cool oil somewhat, and this will result inno change in position oi arm 252 at first but will cause the valve 2,53 and stopper 254 to move to the right. Movement of 254 'to theright will either close the valve completely or close it partially. It it only closesjitpartially. the ame will be reduced in size and this will eilect further cooling oi' 233y mostat T.

unburnt gas `to escape." "igniter on.' "fuel on,"

"attempt at ignition second time, etc. Hence subsequent attempts at ignition 1will be made. and if they repeatedly fail to ignite the gas clear across the burner, and if a safety switch is used Other operations or the system oi' Figure 5 include closure of the valve upon flame failure. If the burner should ignite satisfactorily and then continue in operation indefinitely or for a long period. whereupon the gas supply should become exhausted, the first thing that will happen A is a closure. oi thevalv and subsequent reclosure in line 35, the apparatus will eilect a complete shut down.

In Figure 5 there is shown an arrangement whereby a mechanical valve may be operated by my novel control system instead oi the motor or valve hereinbefore previously illustrated. The system illustrates an elongated gas burner with a large number of burner ports 240, with a hot wire igniter or other igniter 223 at`the right end thereof. A pipe 210 has a valve 253 therein which has a stopper 254 that under normal conditions presses firmly against the right vface of pipe 21| and thereby holds the valve closed. A shaft 253 has a slipping sleeve 25| and a spring 234 cooperating with it as has been previously described v in connection with Figures 3 and 4. An arm 252 SS, the latter which may be built vlike is shown in casing 13 of my prior Patent 2.159,58. A heat: ing resistor 2I5 is located close to strip 233 for the purpose of heating the latter. A flexible wire 202 leads current to ann 252.

The operation of Figure 5 is described as follows. When thermostat T calls for heat, current immediatelyflows through heater-.2 5, and simultaneously it flows via the following path: 36- 202-252-256-223-SS-35. The igniter is therefore heated. The heat from heater 2|5 heats blmetallic strip 233'which thereupon moves stopper 255 away from the opening in pipe 21| and admits ilow of gas to the elongated burner 240. The igniter 223 will normally ignite this gas and the 4saine will Spread across the burner and provide further heating of strip 23 3, As strip 233 becomes hotter, the stopper 254 will move to the left as far as it can whereupon further tension in strip 233 will result in counterclockwise rotation of arm 252 and breakage ot the ignite:- clrcuit. The strip 233 will continue to be heated under the iniluence of two heat sources namely heater 2|5 and the llame. As strip 233 becomes hotter, it will move arm 252 further counterof the igniter contacts 25M-256. vIi' the gas supply is renewed in the meanswhile and begins to exert pressurein pipe 21|,it cannot flow until a substantial time has elapsed from the time it orginally stopped. and not until the igniter has again been energized. When the igniter is reenergized lay-'thermostat T the heater 2|5 will heat strip 232 and reopen the valve.

Should the apparatus be started from a, normal ofi position and the valve 253 open in the normal way but the gas fail to ignite, thevlong current drain that willensue due to that consumed by igniter 223 will cause safety switch SS to shut down the circuit and permit heater 2|5 to cool. This cooling action will reclose the valve and a permanent shut down accomplished. The safety switch SS is so adjusted that the current drawn by heater 2li alone is insufcient to operate SS, but combined extended current drain o! 2 i5 and 223 will cause switch SS to operate.

In event the gas is ignited by igniter 229 of Figure 5, but fails to spread across the burner, the apparatus will shut down as has been said.

Passing now to Figures 6 and 'I which illustrate still another form of my invention, there is provided a supporting insulator |00 from which two bimetallic strips I|0 and |33 are suspended. These bimetallic strips support an insulating block I llwhich is substantially square when viewed as in Figure 'I and which is fairly thick asv shown in Figure 6. Mounted on insulatingblock there is a metal plate II3. To show the shape o1' plate l i3. I have designated the various corners of it with reference numbers ||3a, ||3b, ll3c, "3d, li3e, "3f, "3g and |I3h respectively. It is clear therefore that this metal plate has a slot in it. this slot being designated 'as |50. Rlgidly mounted within insulating block I I i is the metal cylinder |21. 'Cylinder |21 has a. central hole therethrough which is slightly larger than the metal rod |23. The metal rod |23 has a diameter smaller than the width of the slot i50- so this ro'd never touches plate H3, but the rod |29 hns a ange ||4 on its right end which flange is of larger diameter than the width oi' slot |50 and consequently the face of this iiange will from time to time touch plate H3 as will hereinafter appear. On the right tace of flange lll. is mounted contact point ll5. n the left end of rod |20 is mounted a contact point |20. 'I'he rod |20 is longer than the combined thickness oi' block and plate lll for a purpose that willappear. A wire |28 is connected to bimetallic strip |30 which in turn ls connected to one side of the 110 volt line, is connected to metal cylinder |21, and hence to rod |29. The rod |29 is therefore at all times at the potential of one side of the 110 volt A. C. line Sli.l

'Ihere is another set of parts now to be described that are mounted independently from the parts already described, but the parts allV cooperate. Two brackets lll and |24 are rltidiy mounted and always remain in the samerelative position with respectto support |00; Brackets l0 and 24 respectively have downwardly extended plates ||8 and |23. Each of these plates 'Ill and |22- have holes in them slightly larger than the rods lll and |22. Hence rods ill and |32 may freely m and sets the rientmost position that the rigid carriage comprising |22, |22, |2l, |20, and lll may take. The bimetallic strips 0 and |30 are so placed in tension thatthey assume the position shown and in the normal oil? position press the block toward the right and thereby maintains plate lll pressing tightly against plate H2, and presses contacts ||5 and ||6 tightly together. These latter contacts carry no current, but do initially make mechanical contact under pressure.

The electrical circuit of the apparatus of Fisure 6 includesa pair ot wires 25 and 35 for connection to the source of current, a hot-wire or other igniter 20|, a heater |00' arranged nearby strips ||0 and |00, and a motor M or gas valve.

When the room thermostat T calls for heat, the initial current path may be traced as follows: 35-20l--i04-lI0-Il2-Lll3-l|l|20|21 |2B|303B. Since the motor M is connected to |24 at one side, no current ows in the motor at present, hence the motor does not start at this time, but the lgniter 20| is fully energized. The heater |04 soon heats strips ||0 and |30 until it causes them to move carrying block to the left. The arrangement ||`|=|20|2||22|32 remains xed for the time being, however. As block moves to the left it is obvious that the igniter circuit remains closed for the time being since plate Hl remains in contact with plate lll as block moves. After 'a short movement of block contact |26 meets contact |25 and closes the circuit to the motor or valve M. Current flows then in two paths, one similar to that described at the beginning of this paragraph and another as follows: 35--T-M-l24-l23-I32- |25|26|20|2`l|28|3010. Hence the valve M and ignlter 20| remain energized simultaneously for a short while, long enough for the fuel to ignite. Ignition of the fuel causes the bimetallic strips ||0 and |30 to thereupon begin to move very rapidly and the further motion carries block to the left and the pressure set up beasoaovs deenergizing the current circuit to the igniter.

When the block lll has moved to the lett far enough that the left end of cylinder |21 meets the right face of contact point |28, any further movement of the block Ill results in pushing the whole assembly (except IIB, H0, |23 and |20) to the left. During this process the rods |32 and ill slip through strips |23 and IIB respectively to a degree depending upon the temperature reached by 0 and |20.

A iter lon and continued operation of the burner. shoul the name go out. the bimetal strips IIO, |30 woul reverse their motion and contacts |25 and |25 would promptly within a few seconds separate thereby shutting down the motor M.

Further cooling of strips ||0 and |30 would,

promptly take piace until contact points ||5 and ||0 engage and still further cooling will result in slippage between |21 and |20 while the plate lll comes into contact with flange llt thereby reenergizing the ignlter`20| and heater |04. Heater |04 will againpromptly heat strips ||0 and |00 to again carry block to the lei't and again close contacts |25, |26, thereby reciosing the motor circuit and establishing a flow of fuel at ignlter 20|, the latter being subse quently deenergized upon further expansion of strips H0 and |30.

t lng sequence will .take place.

,plate H3, the block Ill will move to the -left tween contacts |25 and |20 causes rod |23 to Assuming that upon starting from an initial oii condition, or starting after a flame failure. the gas fails to ignite, or fails to ignite clear across the burner (when the igniter 20| is located at one end of an elongated gas burner and the blmetals ||0|30 at the other end) the follow- With ||4 touching closing contacts |25 and |26 starting motor M. Even though the llame fails to ignite the heater |04 will prove to cause still further leftward swing of block to break the circuit between plate ||3 and flange lll and thereby deenergize the isniter and heater |00. The heater |04 and blmetalllc strips ||0, |30 will thereupon promptly cool and carry block to the right. breaking contacts |25, |20 thus shutting down the motor M. Further motion to the right will cause engagement oi' contacts |I5 and H6, and reclosure oi' contact between plate IIB and flange ||4. 'I'hus the ignlter and heater |04 will be reenergized and block will travel to the left again until contact is again made at |25, |26 restarting the motor. Further motion to the left will break the igniter circuit thus causing motion to the right to break the motor circuit and reclose the ignlter circuit. The sequence is as follows: ignlter on." "motor on," ignter off," motor oil." igniter on," "motor on," igniter off," "motor oil'," ignlter on," "motor on. "igniter o motor oil," lgniter on," etc. and this sequence will repeat indefinitely.

The advantages of the foregoing sequence are many. One advantage resides ln improving the probability of the igniter 20| initially igniting the gas. After a long shut down, the mixture coming out of the burner is a poor one for ignition and lt plays upon the igniter. Passage oi this poor mixture across the ignter cools the igniter below igniting temperature and the fuel fails to ignite as long as the ignter wire is so cooled. Il' the fuel now is stopped and later restarted, a better mixture is available and it strikes the lgniter while the igniter is at full temperature and ignltes: whereas if vthe fuel had continued to flow without interruption the flow oi' gas across the igniter would continue to keep the igniter4 cooled below ignition temperature.

Another advantage of the repeated on-and-o action in connection with an elongated burner. is' that in such a burner the fuel does not always ignite at all' ports clear across the burner. Design of burners necessitates spacing between the .burner-ports such that often the gas ignites at one end and begins to spread.' 'Ihe velocity of spreading tends to carry the flame along the .burner'to all port' but sometimes conditions are such that the llame only lights at one end-of the burner and fails to spread, or spreads only half way. This means there is an escape of gas from 'the portion of the burner that receives no is# nition. Once the burner has ignited only half way it rarely carries over to the other half unless :it did so as partof one complete' spreading action initially." By the on-and-oif action of my control system, the repeated attempts soon cause the burner to shut down and start up enough times that it' does spread clear across theburner.

'An examination 'of Figure 4 shows that the block 8S moves proportionally to the temperature of the burner and thereby readily responds to overheating. The block i2! of Figure 6. the arm 52 of Figure 3. the arm 252 of Figure 5, and

4 the block ll of Figure 1 all likewise move in proportion to the temperature and excess movement of them likewise indicates overheating. Since 'the specifications are illustrative only and the showing of Figure 4 clearly teaches how overheating controls may be applied to these other blocks, no specific showing has been made in the 'other figures. particularly since the overheating featureis not an essential featureto all of the claims.

As 4further illustration of another feature not essentialto all of the claims is the re-igniter I4. It is omitted from Figuresii to G'since its adaptation thereto is obvious, and is fully taught 'in connection with such systems .by Figure l.

Figures 4 and 5, inserted as illustrative. show the desirability of locating the igniter at the far end of the burner from the thermal element: likewise the use of the control system on a gasolineor oil burner is shown in Figure l. In the light of these showings,` it is clear that any of the systems could be applied to any of these, or any other form of burner. v.

While the several forms of this invention show as a preferred form valves and motors, which are equivalents so far as the claims are concerned, which completely stop the fuel when deenergized, in its broadest aspects the invention is not limited to complete stoppage of the fuel, since partial stoppage, i. e. reducing, will be of some advantage. the intermittent starting method a repeated reducing of fuel flow will have at least as important an advantage as complete stoppage; in fact, in some respects it is of advantage over complete stoppage. Similarly in event the fliel supply should cease for a short interval, the apparatus will recycle that is stop the fuel flow until unburnt gas escapes and then reignite the gas. Reducing the now will prevent as much escape as would otherwise occur.

One feature of Figures l, 3 and 5 is that the valve is'c'ontrolled due to reversals in temperature whereas the igniter is controlled at a low constant temperature. Hence if the fuel supply should For example in igniting the burner by excess of the heat-retaining time of ceramic I4) the quick action of the valve will be accomplished inasmuch as it is controlled by "reversal in temperature; whereas time will be allowed for unburnt gas to escape before the igniter is reenergized. The same is true when ceramic I4 is omitted.

While Figures 1, 3, 4, and 6 have no means to bias the sliding action, Figure 5 has a small spring 300. This spring is desirable t0 assist in the construction of the valve as it eliminates the necess" of' a joint between strip 233 and stem 253.. Such spring Aexerts such a small bias on the sliding members 25B, 25| that it may be neglected. It may be omitted entirely.

I claim to have invented:

l. In combination, a burnerjan electrical heatlng device including a fuel lgniting portion associated with said burner, and control means comprising; heat sensitive means responsive to the heat of combustion at said burner for controlling the feed of fuel to said burner and for controlling the energization of said heating device, said heat straining means so located that after suiiicient motion ofsaid thermal element as to establish flow of fuel the thermal element will exert a force on said restraining means to thereby place stress in the thermal element; said control means including a slidable element associated with and subject to the stress set up in said thermal element due to engagement with said restraining means and including means whereby upon substantial stress in said thermal element the slidable means will vslide and tend to relieve such stress, and means operated by the slidable elementv to control said heating device to deenergize the heating device when the slidable element first begins to slide under the initial stress placed in said thermal 4 elementdue to engagement with said restraining means.

2. In a heating system, a burner, an igniter for the burner, fuel feed control means cooperating with the burner, thermal means located in the high temperature region near the burner, first and second control devices associated with and operated by said thermal means, the first control device including means whereby itis operatively controlled by changes in direction of response of the thermal means whereby to be operatedby changes in the direction of response of the thermai means from a rising temperature to a falling temperature irrespective of the actual temperature level and the second control device including means operatively responsive to the actual temperature level of said thermal means, and means connected with said rst control device -to operate the fuel feed control means and admit fuel as long as the temperature of said thermal means is increasing and to promptly reduce fuel feed when the temperature of said thermal means reverses from a rising to a falling temperature irrespective of the actual temperature level, and means connected with and operated by the second control device to energize said ignter as long as the temperature of said thermal means is below a predetermined low burner temperature as acquired during the starting period of the heating system and to maintain said igniter deenersized as long as the temperature of said thermal means is above said predetermined low burner temperature; whereby in event the burner is operated continuously to a high temperature and the. fuel supply ceases for a short interval to supply fuel to the heating system after which interval fuel is again made available to the heating system, the temperature in said region will drop slightly thus causing a reversal in` the direction of response of said thermal means to thereby promptly stop feed of fuel by the fuel feed control means thus preventing or reducing continued escape of fuel and allowing a long interval to elapse during which unburnt fuel may escape before said igniter is reenergized by said second control device due to drop in temperature below said' predetermined low temperature.

3. The heating system of claim 2 in which the first control device .is so adjusted as not to admit fuel upon starting of the' heating system unless at least a portion of said thermal means is heated. and means for initially supplying heat to said portion oi' said thermal means .whereby to start the system.

4. The heating system of claim 2 'in which said thermal means' consists of a single expansible and contractible thermalelement for-mechanically driving said iii-st and second control devices; the first control device being so adjusted as to prevent feed of fuel until heated initially, and an electrically operated heater controlled by said second control device for energizing and deenergizing the heater to supply heat to said thermal means concurrently with the heating of said igniter.

5. In a heating system, a main fuel burning heater. a fuel feed line to said heater, electrically operated means cooperating with said fuel feed line to control'ow of fuel therethrough, an electrical igniter for the burner, and a control sys tem including the following parts all located wholly within the high temperature region nearby said burner and compactly related therewith as a unit. a thermostatic element movable under the influence of heat, supporting means, movable means mounted on said supporting means so as to be movable with respect thereto and in frictional contact therewith, means connecting the thermostatic element with said movable means so as to move the same against the frictional forces lexerted by said supporting means, contact means in -series with said electrically operated means for directly controlling the same to admit flow of fuel upon initial movement of said movable means and for reducing feed of fuel to said burner upon reversal of direction of movement of said movable means .with respect to the direction of its initial movement, and additional contact means for directly controlling said igniter to deenergize the same shortly after the initial movement of said movable means and to rcenergize the igniter upon substantial reversal in direction of the movable means and travel in the reverse direction of the movable means to a degree greater than that requird to reduce the feed of fuel, said contact means and said additional contact means being mechanically connected to said movable member so as to be depending on its movement to effectuatetheir respective con tact controlling operations.

6. In a heating system, a burner, an igniter for the burner situated to ignite the burner, an expansible and contractable thermal element subject to the heat from the burner. first and second lost-motion connections directly associated asesora with said element, said lost-motion connectionsv including means that tend to relieve the stress that isset up in said element duc to motion thereof resulting from expansion, the rst connection being adjusted to slip more readily than the second and including means for limiting the motion and thereby 'limit its extent of slippage, the second connection being arranged to relieve means controlling said igniter in accordance with the direction of motion of the second connection.

7. In a heating system, an elongated burner having a plurality of ports with adjacent ports positioned close enough together as to normally ignite each other but under abnormal conditions all of the ports do not always ignite from the others,.an igniter situated at one end of said burner, a valve controlling feed of fuel to Said burner. a thermal elementsituated at the end of said burner opposite said igniter and op eratively related to said valve and including means for opening the valve when the thermal element is heated and for closing the valve when the thermal element is cooled. and means which during the starting period of the heating system supplies heat to said thermal element for u. limited period onlyl whereby il' the burner does not ignite at all of its ports between said igniter and thermal element the valve will be closed upon expiration of said limited period.

8. 1inv a heating system, a burner, an igniter for the burner, an electrical circuit controlling said igniter, a thermostatic control comprising a single .expansible and contractable driving member responsive to heat from the burner and a mass 4which cooperates with said member and is driven by one end of said member, said thermostatic control including means whereby the movement of said mass is an unbiased slipping movement so the mass will move with respect tothe vother end of the member and will remain in the position where the member ceased, to exert a force on thesame, and means operated by the thermostatic control for controlling the admission of fuel to said burner and the energizetion of said circuit, the last-named means including means for admitting fuel upon initiation of driving force on said mass by said member due to heating of the member and subsequently deenergizing said igniter upon movement of Asaid mass due to heating of said member and for preventing fuel flow when the member begins to cool and thereby ceases to exert a force on said mass in the direction of the initial force and subsequently reeneiglzingv said igniter upon motion of said mass in the reverse direction from its initial movement, and heating means for initially heating said member to effectuate the initial force.v

9. The system called for by claim 8 in winch the heating means is electrically operated and is connected to said circuit to thereby be operated concurrently .with said igniter, said heating means being sufiiciently large that it supplies enough heat to said member so that upon cooling o! the burner alter accidental extinguish; ment oi' the flame the heating means will heat the member sudiciently to exert force on said mass and reestablish fuel flow whereby to reignite the burner.

l0. Ina heating system. a burner, an igniter for the burner. a single thermal element responm8993378 Y sive to heat from the burner, means associated with the thermal element to affect fuel feed to said burner and to control said igniter; said 4means including means to admit fuel now ,to

said burner upon receiving response from said thermalel'ement indicating heating ofthe latter and to d eenergize said igniter upon receiving further response from said thermal element indiy thereby admit fuel flow. and including means for ceasing suchheating for a short interval and again heating said thermal element to again admit ilow of fuel if ignition does not take place on the rst eort.

ll. The .combination with a control system including first and second devices to be controlled the ilrst of which is to be controlled by operating between rst and second positlom. of a timing device for operating said devices comprising. thermally actuated means which operates upon change in temperature to move in a first direction and thereby move the first device from its first to its second position, heatingmeans for heating said thermally actuated means,

-means whereby upon said first device reaching -heating means being so constructed and connected as to be reenergized when said thermally actuatedmeans has cooled further whereupon the thermally actuated 'means is again heated to re-move said -first device from its ilrst to its second position, said control system having its second device connected to and operated concurrently with said heating means.

l2. The combination with a burner of the control system and timing device of claim 1l in which the said first device mentloned'in claim ll is the valve for the burner which valve is closed when the device is in its said iirst position and the valve is open when the device is in its said second position; and in which the second device is to bev controlled as mentioned in claim 11 is an electrical igniter for the burner.

13, In a heating'system, a burner. an igniter for the burner, a reference member, a mass arranged to move relative said reference member and restrained from motion with respect thereto principally byfrictlon. means cooperating with the mass and as a result of such cooperation to control the admission ol fuel to said burner and the energization of said igniter. said means including an expansible and contractable thermal element for moving said mass relative to said reference member to relative positions depending on the temperature of the thermal element. said thermal element being positioned responsive to heat from said burner, said first-named means also including means for initiating fuel flow to said burner when said thermal element begins to exert a force due to expansion thereofupon the mass to tend to move the same and for subseend of which is carried by said suppczu'tingmeans.`

quentiy deenergizing said igniter upon substantial motion of said mass relative to its reference member and after long and continued operation of the system should thetlame become accidentally .extinguished to first prevent further fuel iiow in response to-change in the direction from expansion to contraction of said element and to reenersize the isniter only after substantial Vmovement of said mam relative said reference member due to contraction of said element. and means for initially heating said thermal element to start generation of heat by the system.

, 1 4. A heating system comprising, a first device constituting a supporting means. a second device adiacent the first device and comprising an expansible and contractable member the first a third device adjacent said second device and constituting afuel controller operated by the second end of said member when the member moves. a fourth device adiacent said third device and including restraining means for oilering resistance to motion' of said fuel controller after movement oi the .fuel controller by said member due to heating of the member, and a fifth device for supporting said fourth device, two of `said .adjacent devices'being mounted relative to each other so that these-two devices` will slide unbiased with respect .to each other to relieve stress'set up in the devices due to forces therebetween resulting from heating of said member, a burner in heat 'transfer relationship with said expansible and contractible member. a fuel feed line to said burner. means associated with said fuel vfeed line for. ailecting the flow oi' fuel therethrough, the 'last-named meanpmcludmg said fuel controller for operating the same to admit fuel when said fuel controller is operated by said member due to heatingthereof and to prevent fuel from flowing when said fuel controller is operated by said member in response to cooling o! the latter, an electrical igniter for the burner. and contact means cooperating with the said two devices that slide with respect to each other for controlling said igniter by deenergizing the latter in response to sliding initiated by heating oi' said member and for reenerg'iaing said ignlter in response to sliding in the opposite direction initiated by cooling of Asaid member; the heating system including means for heating said member initially whereby to start the system.

l5. In a heating system. a burner. an igniter for the burner, heat sensitive means responsive to heat from the burner and including an elongated driving element having first and second ends that move with respect to each other when said heat sensitive means is heated and when it is cooled. a first device which supports the rst end of said element, a second device which offers resistance to the second end of`said element after said second end has moved a short distance as result of heating of said heat sensitive means, one of said devices Abeing a slidable device movable, and restrained by friction so it will slide unbiased when said element continues to move due to heating, whereby the sliding will relieve forces set up in said device and enable quick reversal of the motion' of the second end of said element with respect to said second device upon change from heating to cooling of said burner, fuel controlling means operated by the relative motion of said second end with respect to said second device to admit fuel when said second end is exerting force on said second device and preventing said iiovcr when said second end ceases to exert a force 0n said second device, and means laid igniter comprising contacts operated by said slid- Vingdevice'tocleenergizetheigniterasresultEl;

stitute jets of name which normally ignite the entire burner when it is ignited at one point'only.

means lfor xenium s unites portion of ma 1g 20.Inaheatingsystem.anxedburner.an

burner only-including'an igniter of limited sise. and means for admitting normal fuel now for a 'short interval only and then reducing'fueliiovv forashortintervalonlyandthenagain tting normal fuel iiow for a short interval 17. In a heating system, a burnerzan ter for the burner. a valve. and a control system comprising the following elements alilocated in close proximity with the burner and all subject to the high temperature conditions thereof. an expansible and contractable member one end oi.'

- which moves under iniiuence of heat to open said valve and moves under inuence of coolingto close the valve. a sliding `element connected to said member and arranged to slip unbiasedA and relieve the stress set up in said member due to expansion thereof, d contact means associated with the sliding me ber tocontrol the energination of said igniter to deenergize the same when sliding begins and to'reenersire the same 'in re.- sponse to sliding in the reverse direction.

18. In a. heating system. a burner, lheating means including an igniter for the burner, an electrical valve controlling fuel feed to said ',tively operated by the thermal element andthe sliding member for respectively controlling said valve and igniter.

'headers 19. In a heating system. a burner. a fuel controller'ior admitting and reducing fuel now to the burner. a sliding member which may slide unbiased. a thermal element initiallyout of engagement with said member but which moves into engagement therewith when heated, said thermal element being positioned nearby the v burner. additional means for initially heatingsaid element, means Vfor operating said fuel controller l0 to admit fuel when said element moves into engagement with said member, and overheating-V responsive means i'oroperating the fuel controller 'to reduce fuel flow in event said member moves inexcess of a predetermined amount.

igniterior the burner,V fuel control means for the burner. a thermal element responsive to heat ffrom the burner, means responsive 'to the direc.-

tion of motion of said element for controlling n' said fuel control ineens, and means responsive 2l. In a heating system, a burner, a fuelcontroller forthe burner, a first member. a sliding member frictionally in contact with the iirst member which may slide with respect thereto when a force is exerted on the sliding member, thermal force producing means.responsive to combustion at said burner which produces aforce as a result of heating will not move said sliding member. and that substantial movement of said thermal force producing means d ue to heating .1 thereof following substantial initial movement will move said sliding member with respect to said iirst member, overheat-responsive means to operate said fuel controller to reduce fuel ilow when said sliding member moves a predetermined amount with respect to said first member in said ilrst direction, means for operating said fuel conl trolier to admit fuel when saidthermal force producing means is exerting a force on said sliding member in said first direction, and means for initially heating said thermal force producing means to a suiilcient degree to exert'aforce on said sliding member to start ilow of fuel. i

WILLIAMD. HALL. 

